1. Field of the Invention
The present invention relates to a vibration-damping rubber composition to be used as a material for a rubber member (chamber wall) of a liquid-filled vibration-damping rubber device for use as an engine mount, a suspension bush or the like in an automotive vehicle, and to a liquid-filled vibration-damping rubber device produced by using the vibration-damping rubber composition.
2. Description of the Related Art
Vibration-damping rubber members such as an engine mount and a suspension bush, which are used as joint members for connection between various components such as an engine, a frame and the like in an automotive vehicle, exhibit a vibration-damping capability attributable to the spring property and the vibration attenuation property of a rubber body (vulcanized molded rubber body) thereof. In recent years, various types of vibration-damping rubber devices of a liquid-filled type (liquid-filled vibration-damping rubber devices) have been proposed which are further improved in vibration-damping capability over these vibration-damping rubber members by filling a liquid in the rubber devices (see, for example, JP-A-HEI5(1993)-140579 and JP-A-HEI7(1995)-301278).
Such a liquid-filled vibration-damping rubber device includes a rubber member (chamber wall) which is deformable according to inputted vibrations. A glycol liquid such as ethylene glycol is sealingly contained in a sealed space defined by the rubber member (chamber wall). In general, the rubber member is formed from a rubber composition prepared by blending a plasticizer and other substances with a rubber component such as a natural rubber or a styrene-butadiene rubber (SBR).
However, the plasticizer to be blended in the rubber composition is not very compatible with the rubber component such as the natural rubber and, therefore, liable to leach into the glycol liquid contained in the sealed space. Disadvantageously, this may result in increase in the hardness of the rubber member (chamber wall) after thermal aging, deterioration of vibration-damping capability, and reduction in durability.